In recent years, substantial interest has grown in the bookbinding, publishing and printing industries, and in the graphic arts area generally with respect to the development of improved adhesive compositions which lend themselves to bookbinding processes.
Casemaking refers to the production of the case or cover, i.e., the outer shell, of a hard bound book. During this process, the material that forms the outer covering of the book is bonded to binder boards to form a “hard” cover. Typically, the covering material is passed along a conveyor during which time binder boards are mated onto the adhesive coated covering material. The surplus covering material is folded over on to the binder board in a two step process known as “turning in” in which either the sides are folded in first and the ends are folded in second resulting in an overlap of the ends over the sides, or the ends are folded in first and the sides second.
In bookbinding processes, a number of “signatures”, i.e., sheets of paper, are stacked together to form a book block which is held together by a clamp. The book block then has its spine area cut to remove any folding in the sheets that has resulted from the stacking process. The book spine then has spine glue applied to it. The spine glue may be a hot melt adhesive, an aqueous adhesive or a reactive hot melt adhesive. A primer may optionally be applied to the spine prior to application of the glue. The purpose of the primer is to ensure better adhesion of the spine glue to the spine. Once the spine glue has been applied, the cover material is then added to the book block to create the bound book.
For a hard cover book, the bound book block is then typically subjected to a conventional rounding process in order to round the spine of the finished book. One of the difficulties encountered with rounding reactive hot melt bound books off-line is that a significant amount of heat is required to soften the adhesive once cured. For rounding books on-line before the reactive hot melt adhesive has cured there are difficulties in retaining the rounded shape due to the slow crystallization of the adhesive as it cools.
During the casing-in process, the rounded book block is laminated to the inside of the cover (case) of a hard bound book by coating the outside of the end sheets of the book block with the adhesive, and then bonding the cover to the end sheets.
There is thus a need in the art for a system that can be used in bookbinding process wherein bound books can be subjected to a rounding process either on or off line without the use of extra heat or risk of the round relaxing.